The major purpose of this research project is to describe the physiological mechanisms that control the suppression of ingestion in the suckling rat. Ingestion of milk can be suppressed by preloading the gastrointestinal tract with solutions that vary in caloric density, osmolality, and volume. The properties of the preload solution necessary or sufficient for suppression have not been clearly identified. In addition, the precise site of action (stomach, intestine) and the nature of the suppression signals (neural, hormonal) are not known. Acute surgical techniques were developed to investigate the short-term controls of ingestion. They include (a) pyloric ligation which prevents food from leaving the stomach, (b) gastric by-pass which passes food from the esophagus directly into the intestine without filling the stomach, (c) vagotomy which eliminates signals carried by parasympathetic nerves that supply the stomach and intestine, and (d) spinal cordotomy which eliminates signals carried by splanchnic sympathetic nerves that supply the stomach and intestine. By measuring ingestive behaviors after loading the stomach or intestine in denervated or normal pups, it will be possible to determine the contribution of each compartment of the gut to the control of ingestive behavior. Ultimately this research is designed to increase our understanding of the controls for ingestion, appetite, and regulation of body weight in normal infants as well as obese infants.